I just finished U:GA... AWESOME GAME!!! I just want to know if i lend the game to a friend and he formats the cartridge to earn trophies, will i lose my collectibles or are they saved in my Vita??
He has his own memory card right ?
Your Vita has no internal storage. All your game saves and data will be kept in your own memory card. Keep your own men card, and ask him to get his own.
If a game saves to the *game* card (i.e., the Uncharted game card) itself, then your friend just have to be careful not to overwrite your files.
EDIT: If you're really good friends and want to share a men card, I supposed you can backup your mem card to a PC/Mac/PS3, and then restore it over his data later. But it's a dog slow process.